Aerial Variometer for Wireless Sets No. 19 MK. II 12440-PHILA-44

Wireless Sets No. 19 Mk II Aerial Variometer: Aerial Variometer matching the british Wireless Set No. 19 Mk II.

The Aerial Variometer was used to match a short rod aerial of 8 or 12 ft to 1/4 wavelength in the frequency range of the W.S. No. 19. On the "low band" (2 - 4,5 MHz), the 0 - 100 calibration is used, the two coils are switched in series and inductance had to be added; in contrast in the "high band" (4,5 - 8 MHz), the coils were switched in parallel, the inductance was reduced, the calibration 200 - 100 is used. The control can be rotated 360°, switches at the 180° positions of the control knob switch the coils in the correct operation.

Variometers must principally be of the same Mark as the Wireless Set No. 19:

Wireless Sets No. 19 Mk I Aerial Variometer: the adjustable resistor R29A had to be factory adjusted to adjust the meter reading, it is placed in the set.

Mk I variometers can only be used with W.S. No. 19 Mk I.

Wireless Sets No. 19 Mk II Aerial Variometer: the adjustable resistor R29A is placed in the variometer itself, the Mk II variometer can be used with W.S. No. 19 Mk II. A variometer Mk II can be used with W.S. No. 19 Mk III, but the R29A might have to be readjusted for correct meter readings.

A variometer Mk II can be used with W.S. 19 Mk. I, but the R29A within the set has to be short-circuited.

Wireless Sets No. 19 Mk III Aerial Variometer: the adjustable resistor R29A is placed in the variometer itself, the Mk III variometer can be used with W.S. No. 19 Mk III. A variometer Mk III can be used with W.S. No. 19 Mk II, but the R29A might have to be readjusted for correct meter readings.

A variometer Mk III can be used with W.S. 19 Mk. I, but as above mentionned, the R29A within the set has to be short-circuited.

(see L. Meulstee WfW p. W.S.19-27 for schematic and details).

The Wireless Sets No.19 Mk II Aerial variometers have been produced in United Kingdom and und the U.S. (contract 12440-PHILA-44).

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